Power plants burning fossil fuels are large emitters of carbon dioxide. Coal and natural gas are the most widely used fossil fuels for power generation worldwide and in the US. When burned, coal of various types releases more CO2 per unit electricity generated than other fossil fuels including natural gas. As a result, coal-fired power plants have the highest CO2 intensity (CO2 emissions per unit of electricity output) of all thermal power plants.
On the other hand, natural gas-fired, combustion turbine based power plants have lower CO2 intensity than coal-fired plants. However, gas turbine (GT) exhaust typically has low CO2 concentration (4-5% vol) and high oxygen concentration (13-14% vol), compared to 12-13% CO2 and 5-6% oxygen for typical coal-fired power plants. The low CO2 concentration of GT exhaust can lead to large equipment size and capital investment, and high oxygen concentration can result in accelerated degradation of the CO2 solvent and increased operating cost, for a post-combustion CO2 capture (PCC) system for a gas-fired combustion turbine based power plant.
Based on the above discussion, there is a need for new methods and apparatus for reducing CO2 intensity with regard to exhaust gases generated in a gas fired combustion turbine.